Once a LED lamp having a plurality of light emitting diodes is lit up, the LEDs or LED module will rapidly increase their temperature to accumulate heat in the lamp. If the heat is not well dissipated, it may cause flicker and deteriorate the illumination quality of the LED lamp, thereby shortening the service life of the lamp.
U.S. Pat. No. 6,793,374 disclosed a LED lamp having a gear column connected between a cap and substrates. The substrates are arranged as a polyhedron with planar surfaces. A fan is provided in the column for cooling the substrates and LEDs.
However, such a prior art has the following drawbacks:    1. The LED substrates are formed as a polyhedron, which is a closed “housing” to greatly accumulate the heat produced by LEDs in the column, being difficult to dissipate the heat satisfactorily.    2. A fan (9) should be installed in the column for cooling the lamp, increasing the cost of installation, operation and maintenance. It also requires electric energy for driving the fan, wasting energy on a viewpoint of environmental protection.    3. The rotation of the fan may cause vibration of the lamp, possibly damaging the circuit of LEDs or even making short circuit of the LED circuit of the lamp, thereby being inoperative accordingly.
The present inventor has found the drawbacks of the prior art and invented the LED lamp for instantly and effectively dissipating the heat from the lamp.